Xll 



CONTENTS 



Laboratory Exercises . . . . 



Acid soils in the field, I ; Litmus paper with and 

 without potassium nitrate, II ; Litmus paper test, 

 III ; Test for soil carbonates, IV ; Ammonia test for 

 acidity, V ; Zinc sulfide test for acidity, VI ; Incrusta- 

 tion of "alkali" by capillary action, VII. 



PAGES 



122-124 



CHAPTER IX 



The Germ Life of the Soil 125-140 



Microorganisms injurious to crops, § 154 ; Germs 

 not directly injurious to crops, § 155 ; Numbers of 

 bacteria in soils, § 156 ; Conditions affecting bacterial 

 growth, § 157 ; Air supply, § 158 ; Moisture, § 159 ; 

 Temperature, § 160 ; Organic matter, § 161 ; Soil 

 acidity, § 162 ; Bacteria in relation to soil fertility, 

 § 163 ; Action on mineral matter, § 164 ; Decom- 

 position of non-nitrogenous organic matter, § 165; 

 Decomposition of nitrogenous organic matter, § 166 ; 

 Ammonification, § 167; Nitrification, § 168; Effect 

 of soil aeration on nitrate formation, § 169 ; Effect of 

 temperature on nitrate formation, § 170; Effect of 

 sod on nitrate formation, § 171 ; Depths at which 

 nitrate formation takes place, § 172 ; Loss of nitrates 

 in drainage, § 173 ; Denitrification, § 174 ; Nitrogen 

 fixation, § 175 ; Nitrogen fixation through symbiosis 

 with higher plants, § 176; Soil inoculation for le- 

 gumes, § 177; Nitrogen fixation by free-living 

 germs, § 178. 

 Questions on Chapter IX ...... 40 



Laboratory Exercises . . . . . . . 140-142 



Test for nitrates in soil, I ; Test for ammonia in 

 soil, II ; Factors affecting nitrate formation, III ; 

 Examination of legume nodules, IV ; Examination of 

 nodule bacteria, V; Soil inoculation, VI. 



CHAPTER X 



Soil Air and Soil Temperature .... 143-152 



Soil air contained largely in non-capillary spaces, 

 § 179 ; There may be too much or too little soil air, 



